Pityriasis lichenoides, an immune complex disease?

Nine biopsies from skin lesions of 5 patients with pityriasis lichenoides acuta and three biopsies from skin lesions of 3 patients with pityriasis lichenoides chronica were examined by means of the direct immunofluorescence technique. IgM deposits along the dermoepidermal junction were found in only two biopsies. In the majority of bioipsies, complement (C3) deposits were found along the dermo-epidermal junction and in the vessel walls. Immunoglobulin and C3 deposits were not found concomitantly in the vessel walls.